It is at light heavyweight that his record really shines. In all he defeated 7 lineal light heavyweight champions.

At heavyweight he beat most of Jack Dempseys title challengers.

He was a middleweight but he had to suffer to make the weight.

I remember Ted Carroll pointing out that both Greb and Walker did better than any other middleweights against bigger men, but that both stumbled some against men their own size or smaller. Could be weight making, or perhaps speed gave them problems.